Reverse HideBottomViewOnScrollBehavior and initialize to hide state android

Reverse HideBottomViewOnScrollBehavior and initialize to hide state android - android

I have a CoordinatorLayout with a RecyclerView and a Fab button.
<androidx.coordinatorlayout.widget.CoordinatorLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<androidx.swiperefreshlayout.widget.SwipeRefreshLayout
android:id="#+id/swipeChatRoomRecycler"
android:layout_width="match_parent"
android:layout_height="match_parent">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/chatRoomRecycler"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clipToPadding="true"
android:scrollbars="vertical" />
</androidx.swiperefreshlayout.widget.SwipeRefreshLayout>
<com.google.android.material.floatingactionbutton.FloatingActionButton
android:id="#+id/bottomScrollFab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="bottom|end"
android:layout_margin="12dp"
android:src="#drawable/ic_arrow_down"
app:backgroundTint="#color/colorPrimaryLight"
app:layout_behavior="com.google.android.material.behavior.HideBottomViewOnScrollBehavior"
app:layout_anchor="#id/swipeChatRoomRecycler"
app:layout_anchorGravity="bottom|right|end"
app:fabSize="mini" />
</androidx.coordinatorlayout.widget.CoordinatorLayout>
The recyclerView is set as below
viewManager = LinearLayoutManager(activity).apply {
orientation = LinearLayoutManager.VERTICAL
stackFromEnd = false
reverseLayout = true
}
What i want to achieve is
At the launch of the activity i want the bottomScrollFab to be invisible since the recycler is scrolled in the end as by default
I want to achieve the exact reverse behaviour, meaning that i want the Fab to be shown when recycler is not onScroll and to be hidden when recycler is onScroll
How can i do those two things?

Well up to now i have created a custom Behaviour which changes the alpha when the recycler is scrolled. It works pretty fine
class ReverseHideViewOnScrollBehaviour(context: Context, attributeSet: AttributeSet): CoordinatorLayout.Behavior<View>(context, attributeSet) {
override fun layoutDependsOn(parent: CoordinatorLayout, child: View, dependency: View): Boolean {
return dependency is RecyclerView
}
override fun onDependentViewChanged(parent: CoordinatorLayout, child: View, dependency: View): Boolean {
val yPercentage = getViewOffsetFromRecycler(parent, child)
val diff = 100.0f - yPercentage
child.alpha = 1 - diff
return true
}
private fun getViewOffsetFromRecycler(parent: CoordinatorLayout, view: View): Float{
var percentage = 100f
val dependencies = parent.getDependencies(view)
dependencies.forEach { dependency ->
if (dependency is SwipeRefreshLayout) {
val recycler = (dependency.findViewById<RecyclerView>(R.id.chatRoomRecycler))
val offset: Int = recycler.computeVerticalScrollOffset()
val extent: Int = recycler.computeVerticalScrollExtent()
val range: Int = recycler.computeVerticalScrollRange()
percentage = if (range - extent == 0) 100f else 100.0f * offset / (range - extent).toFloat()
}
}
return percentage
}
}
So the FloatinActionButton
<com.google.android.material.floatingactionbutton.FloatingActionButton
android:id="#+id/bottomScrollFab"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="bottom|end"
android:layout_margin="12dp"
android:src="#drawable/ic_arrow_down"
app:layout_behavior=".ui.views.ReverseHideViewOnScrollBehaviour"
app:layout_anchor="#id/swipeChatRoomRecycler"
app:layout_anchorGravity="bottom|right|end"
app:fabSize="mini" />

Related

Horizontal RecyclerView with dynamic item height

I am trying to create a horizontal recycler view with dynamic height by following this stack overflow post. The solution seems working. But the recycler view items disappear when I try to remove an item from recycler view.
recyclerview layout:
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/recyclerview"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="20dp"
android:clipToPadding="false"
android:orientation="horizontal"
android:paddingStart="13dp"
android:paddingEnd="13dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
Recycler view item layout:
<androidx.cardview.widget.CardView
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginEnd="4dp"
android:layout_marginStart="4dp"
app:cardBackgroundColor="#BCAAAA"
app:cardElevation="2dp">
<TextView
android:padding="36dp"
android:id="#+id/textViewName"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:textSize="22sp"
tools:text="Test String"/>
</androidx.cardview.widget.CardView>
Activity:
val flexBoxLayoutManager = FlexboxLayoutManager(this, FlexDirection.ROW, FlexWrap.NOWRAP)
with(recyclerView) {
layoutManager = flexBoxLayoutManager
adapter = RecyclerViewAdapter()
setHasFixedSize(false)
}
Adapter:
class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
var textViewName: TextView = itemView.findViewById(R.id.textViewName)
init {
updateLayoutParamsToAllowHorizontalScrolling()
}
private fun updateLayoutParamsToAllowHorizontalScrolling() {
(itemView.layoutParams as? FlexboxLayoutManager.LayoutParams)?.let {
it.flexShrink = 0.0f
it.alignSelf = AlignItems.FLEX_START
}
}
}
override fun onBindViewHolder(holder: RecyclerViewAdapter.ViewHolder, position: Int) {
val item = listItems[position]
var msg = "Sample item no:$position "
for(i in 0..position){
msg += "dynamic content \n"
}
holder.textViewName.text = msg
holder.itemView.setOnClickListener {
val pos = listItems.indexOf(item)
listItems.removeAt(pos)
notifyItemRemoved(pos)
}
}
A screen recording of the output:
Is there any way to fix this issue? Or Are there any other approach to implement horizontal recyclerveiw with dynamic height?

I have fixed the issue without using FlexBoxLayoutManger.
Used LinearLayoutManager with horizontal orientation and the following code in onBindViewHolder in RecyclerViewAdapter.
holder.itemView.post {
val wMeasureSpec =
View.MeasureSpec.makeMeasureSpec(holder.itemView.width, View.MeasureSpec.EXACTLY)
val hMeasureSpec = View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED)
holder.itemView.measure(wMeasureSpec, hMeasureSpec)
if (holder.itemView.measuredHeight > holder.itemView.height) {
holder.itemView.layoutParams =
(holder.itemView.layoutParams as ViewGroup.LayoutParams)
.apply {
height = holder.itemView.measuredHeight
}
}
}

listview items are not showing when i set the height to wrap or match or 0dp, they only show up when i use specific number

my listview has a relative layout parent, it is set to wrap hight and match width, the problem is in the listview height, when i set it to 100dp it works fine, the items show, but when i set it to wrap or match parent it clips and only show one or non of the items, i can see that there is a scroll bar at the side as well, how can i make it wrap?
<RelativeLayout
android:id="#+id/expandable_rl"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:padding="#dimen/xlarge">
<ListView
android:id="#+id/lisview"
android:layout_width="match_parent"
android:layout_height="100dp"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:layout_alignParentEnd="true"
app:layout_constraintVertical_bias="1.0"
android:layout_alignParentBottom="true"
app:layout_constraintHorizontal_bias="0.0" />
</RelativeLayout>
and this is how i am setting it, its just to test it, its located in a recycler view
holder.list.adapter = ArrayAdapter(holder.itemView.context, R.layout.simple_item, arrayListOf("hello","hi","testing"))
this is how i expand the expandable layout
holder.itemView.setOnClickListener {
if (unitsList[position].isExpandable) {
holder.expandableRL.visibility = if (holder.expandableRL.visibility == View.GONE) View.VISIBLE else View.GONE
}
}
i tried using notifyItemChanged(position) but it made it expand then immediately collapse for some reason
i am new here and don't know how to fix this at the moment

A fully wrapped list means it doesn't scroll, as all of items are visible.
If that is the case, why using a ListView in the first place.
Here is a suggestion to make use of LinearLayout instead.
XML for RecyclerView item:
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="wrap_content"
>
<Button
android:id="#+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintEnd_toEndOf="parent"
android:text="Click Me" />
<LinearLayout
android:id="#+id/expandable_rl"
android:layout_width="0dp"
android:layout_height="wrap_content"
app:layout_constraintTop_toBottomOf="#id/button"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintEnd_toEndOf="parent"
android:visibility="gone"
android:orientation="vertical">
</LinearLayout>
</androidx.constraintlayout.widget.ConstraintLayout>
And Here's the adapter:
class RecyclerAdapter: RecyclerView.Adapter<RecyclerView.ViewHolder>() {
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {
return ViewHolder(
LayoutInflater.from(parent.context).inflate(
R.layout.recycler_item,
parent,
false
)
)
}
override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
(holder as? ViewHolder)?.itemView?.let { itemView ->
val expandable = itemView.findViewById<LinearLayout>(R.id.expandable_rl)
createItems(expandable)
itemView.findViewById<Button>(R.id.button).setOnClickListener {
expandable.visibility = View.VISIBLE
}
}
}
private fun createItems(expandable: LinearLayout) {
listOf("Hi", "Hello", "Goodbye").forEach { word ->
val item = createItem(expandable.context, word)
expandable.addView(item)
}
}
private fun createItem(context: Context, word: String): View {
return LinearLayout(context).apply {
layoutParams = LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT)
orientation = LinearLayout.VERTICAL
gravity = Gravity.CENTER
addView(
TextView(context).apply {
layoutParams = LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT)
text = word
}
)
}
}
override fun getItemCount(): Int {
return 30
}
class ViewHolder(view: View): RecyclerView.ViewHolder(view)
}
This is a basic design, but you can take it from here and design what you need.

Viewpager2 inside Nestedscrollview consist two Fragment with Recyclerview having problem

I made a viewpager2 which has two Fragments, inside each Fragment there is a Recyclerview. The viewpager itself is inside a Nestedscrollview in order to hide the toolbar when scroll up. Here is my code:
<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
>
<com.google.android.material.appbar.AppBarLayout
android:id="#+id/appbarlayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:theme="#style/ThemeOverlay.AppCompat.Dark.ActionBar">
<androidx.appcompat.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="#color/colorPrimary"
app:layout_scrollFlags="scroll|enterAlways">
</androidx.appcompat.widget.Toolbar>
<com.google.android.material.tabs.TabLayout
android:id="#+id/tab_layout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:textAlignment="center"
app:tabGravity="fill"
app:tabMode="fixed"/>
</com.google.android.material.appbar.AppBarLayout>
<androidx.core.widget.NestedScrollView
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:android="http://schemas.android.com/apk/res/android"
app:layout_behavior="#string/appbar_scrolling_view_behavior">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<androidx.viewpager2.widget.ViewPager2
android:id="#+id/pager"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:fitsSystemWindows="true"/>
</LinearLayout>
</androidx.core.widget.NestedScrollView>
<include layout="#layout/material_design_floating_action_menu" />
</androidx.coordinatorlayout.widget.CoordinatorLayout>
As I said the viewPager2 have two fragment each of them have a recyclerview. Here problem is, fragment 2 recyclerView take the same height of fragment 1 recyclerView though both recyclerView have different list items and their height should be depends on the list items. I mean, I am expecting these recyclerViews height should act separately based on the list. How can I solve this issue? Please let me know if you need fragment code.
Edit:
Activity code which holds the viewPager2
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initToolbar();
init();
viewPager.setAdapter(createCardAdapter());
new TabLayoutMediator(tabLayout, viewPager,
new TabLayoutMediator.TabConfigurationStrategy() {
#Override public void onConfigureTab(#NonNull TabLayout.Tab tab, int position) {
//tab.setText("Tab " + (position + 1));
if(position == 0){
tab.setText("Home");
}else if(position == 1){
tab.setText("Events");
}
}
}).attach();
RunnTimePermissions.requestForAllRuntimePermissions(this);
showNotifyDialog();
}
ViewPager Adapter Code:
public class ViewPagerAdapter extends FragmentStateAdapter {
private static final int CARD_ITEM_SIZE = 2;
public ViewPagerAdapter(#NonNull FragmentActivity fragmentActivity) {
super(fragmentActivity);
}
#NonNull #Override public Fragment createFragment(int position) {
switch (position){
case 0:
return HomeFragment.newInstance("abc","abc");
// break;
case 1:
return EventListFragment.newInstance("abc","abc");
// break;
}
return HomeFragment.newInstance("abc","abc");
}
#Override public int getItemCount() {
return CARD_ITEM_SIZE;
}
}
Fragment 1 layout:
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto"
tools:context=".fragment.EventListFragment">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/rv_event_list"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
android:layout_marginTop="16dp"
/>
</FrameLayout>
Fragment 2 layout
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto"
tools:context=".fragment.MedicineListFragment">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/rv_medicine_list"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
android:layout_marginTop="16dp"
/>
</FrameLayout>

Alright buddy. I did it! I have the solution to this issue.
First off, here's the official response from Google after I opened an issue.
https://issuetracker.google.com/issues/188474850?pli=1
Anyway, on to the fix. Replace the NestedScrollView with this class:
https://gist.github.com/AfzalivE/fdce03eeee8e16203bcc37ba26d7abf3
The idea is to basically create a very light-weight version of NestedScrollView. Instead of messing with child heights, we listen to the children's scroll and either let them scroll, or forward the scrolling to the BottomSheetBehavior. For example when the RecyclerView has been scrolled all the way to the top, then it doesn't consume any of the scrolling, so we can forward that to the bottom sheet so it can scroll. And we only allow the RecyclerView to scroll when the Bottom sheet is expanded.
Also, I must add that this scenario works out of the box with Jetpack Compose + Accompanist-pager so just do that if you really need perfect functionality.
class BottomSheetScrollView(context: Context, attrs: AttributeSet?) : FrameLayout(context, attrs),
NestedScrollingParent2 {
private val TAG = "NestedScroll3"
private val childHelper = NestedScrollingChildHelper(this).apply {
isNestedScrollingEnabled = true
}
private var behavior: BottomSheetBehavior<*>? = null
var started = false
var canScroll = false
var pendingCanScroll = false
var dyPreScroll = 0
init {
ViewCompat.setNestedScrollingEnabled(this, true)
}
private val bottomSheetCallback = object : BottomSheetBehavior.BottomSheetCallback() {
override fun onStateChanged(bottomSheet: View, newState: Int) {
onNextScrollStop(newState == BottomSheetBehavior.STATE_EXPANDED)
Log.d(
"BottomSheet",
"Can scroll CHANGED to: $canScroll, because bottom sheet state is ${
getBottomSheetStateString(newState)
}"
)
}
override fun onSlide(bottomSheet: View, slideOffset: Float) = Unit
}
fun onNextScrollStop(canScroll: Boolean) {
pendingCanScroll = canScroll
}
override fun onStartNestedScroll(child: View, target: View, axes: Int, type: Int): Boolean {
// ViewPager2's RecyclerView does not participate in this nested scrolling.
// This allows it to show it's overscroll indicator.
if (target is RecyclerView) {
val layoutManager = target.layoutManager as LinearLayoutManager
if (layoutManager.orientation == LinearLayoutManager.HORIZONTAL) {
target.isNestedScrollingEnabled = false
}
}
if (!started) {
Log.d(TAG, "started nested scroll from $target")
childHelper.startNestedScroll(axes, type)
started = true
}
return true
}
override fun onNestedScrollAccepted(child: View, target: View, axes: Int, type: Int) {
Log.d(TAG, "accepted nested scroll from $target")
}
override fun onStopNestedScroll(target: View, type: Int) {
if (started) {
childHelper.stopNestedScroll(type)
started = false
Log.d(
TAG,
"stopped nested scroll from $target, changing canScroll from $canScroll to $pendingCanScroll"
)
canScroll = pendingCanScroll
}
}
override fun onNestedScroll(
target: View,
dxConsumed: Int,
dyConsumed: Int,
dxUnconsumed: Int,
dyUnconsumed: Int,
type: Int
) {
Log.d(
TAG,
"onNestedScroll: dxC: $dxConsumed, dyC: $dyConsumed, dxU: $dxUnconsumed, dyU: $dyUnconsumed"
)
if (dyUnconsumed == dyPreScroll && dyPreScroll < 0) {
canScroll = false
Log.d(TAG, "Can scroll CHANGED to: $canScroll, because scrolled to the top of the list")
}
}
override fun onNestedPreScroll(target: View, dx: Int, dy: Int, consumed: IntArray, type: Int) {
Log.d(
TAG,
"onNestedPreScroll: dx: $dx, dy: $dy, consumed: [ ${consumed.joinToString(", ")} ]"
)
if (!canScroll) {
childHelper.dispatchNestedPreScroll(dx, dy, consumed, null, type)
// Ensure all dy is consumed to prevent premature scrolling when not allowed.
consumed[1] = dy
} else {
dyPreScroll = dy
}
}
override fun onAttachedToWindow() {
super.onAttachedToWindow()
behavior = findBottomSheetBehaviorParent(parent) as BottomSheetBehavior<*>?
behavior?.addBottomSheetCallback(bottomSheetCallback)
}
override fun onDetachedFromWindow() {
super.onDetachedFromWindow()
behavior?.removeBottomSheetCallback(bottomSheetCallback)
}
private fun findBottomSheetBehaviorParent(parent: ViewParent?): CoordinatorLayout.Behavior<*>? {
if (parent !is View) {
throw IllegalArgumentException(
"None of this view's ancestors are associated with BottomSheetBehavior"
)
}
val layoutParams = parent.layoutParams
return if (layoutParams is CoordinatorLayout.LayoutParams && layoutParams.behavior != null) {
layoutParams.behavior
} else {
findBottomSheetBehaviorParent((parent as View).parent)
}
}
private fun getBottomSheetStateString(state: Int): String {
return when (state) {
1 -> "STATE_DRAGGING"
2 -> "STATE_SETTLING"
3 -> "STATE_EXPANDED"
4 -> "STATE_COLLAPSED"
5 -> "STATE_HIDDEN"
6 -> "STATE_HALF_EXPANDED"
else -> "0"
}
}
}

I do not understand why you have recyclerview inside FrameLayout .
Here problem is, fragment 2 recyclerView take the same height of
fragment 1 recyclerView though both recyclerView have different list
items and their height should be depends on the list items
RecyclerView generally always depends on the item_layout until we have not fixed its height n width to match_parent.
In your case you have fixed RecyclerView android:layout_width and android:layout_width to match_parent in both the Fragment .
Try this:
Fragment 1
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto"
tools:context=".fragment.EventListFragment">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/rv_event_list"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="16dp"
/>
</FrameLayout>
Fragment 2
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto"
tools:context=".fragment.MedicineListFragment">
<androidx.recyclerview.widget.RecyclerView
android:id="#+id/rv_medicine_list"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginTop="16dp"
/>
</FrameLayout>
P.S: assuming each reacyclerView's item_layout would be having height as wrap_content

How do I achieve on scroll behavior where both the toolbar and bottom navigation should hide?Only one of them is working

I am trying to achieve the coordinator layout behaviour where on scrolling the recycler view can hide both the toolbar and bottom navigation view. So far I have achieved one success i.e bottom navigation bottom bar does hide but with one caveat that it remains active even when the keyboard is on(how do I fix that too?)
My main concern here is how do I achieve the same feature of bottom navigation view of hiding into the toolbar?
I have included the custom toolbar in Appbar layout, but I have tried to add the Toolbar layout tag too in the AppBar nothing works, It just remains the same.
And for the bottomnavigation jumping up on top I don't know what to do? till now I have added snap scroll flags on the bottomnavigation view to stop this behaviour and also snap flag didn't work, I think so, coz it remains in halfway position while going up on search tap.
Got this BottomNavigationBehavior from the wonderful article.
reference
video showing behavior
image for snap behavior
activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout
xmlns:tools="http://schemas.android.com/tools"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_height="match_parent"
android:layout_width="match_parent"
>
<com.google.android.material.appbar.AppBarLayout
android:id="#+id/appbar"
android:layout_width="match_parent"
android:layout_height="?actionBarSize"
app:elevation="0dp"
android:background="#android:color/transparent"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
>
<include
app:layout_scrollFlags="scroll|enterAlways|snap"
layout="#layout/browser_search_tap_tb"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="#+id/browser_tb"
/>
</com.google.android.material.appbar.AppBarLayout>
<!--Scrolling effect for the bottom nav menu-->
<androidx.recyclerview.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:listitem="#layout/rv_test_items"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
android:id="#+id/rv_test"
/>
<!--Bottom navigation view for the Selection of the Tabs and Items in Menu-->
<com.google.android.material.bottomnavigation.BottomNavigationView
app:layout_scrollFlags="scroll|enterAlways|snap"
android:id="#+id/browser_bottom_nav_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="bottom"
android:background="#ffff"
app:layout_behavior="com.example.android.browserui.BottomNavigationBehavior"
app:labelVisibilityMode="unlabeled"
app:menu="#menu/bottom_nav_menu"
/>
</androidx.coordinatorlayout.widget.CoordinatorLayout>
browser_search_tap_tb.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.appcompat.widget.Toolbar
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="?actionBarSize"
android:background="#android:color/transparent"
app:layout_scrollFlags="scroll|enterAlways"
app:popupTheme="#style/ThemeOverlay.AppCompat"
app:contentInsetStart="8dp"
app:contentInsetEnd="8dp"
>
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<EditText
android:layout_width="0dp"
android:layout_height="match_parent"
android:hint="Search or type new address"
android:padding="8dp"
android:paddingEnd="12dp"
android:paddingStart="12dp"
android:drawableEnd="#drawable/ic_mic"
android:inputType="textWebEditText"
android:background="#drawable/rounded_et_search"
app:layout_constraintStart_toStartOf="parent" app:layout_constraintTop_toTopOf="parent"
app:layout_constraintBottom_toBottomOf="parent" android:id="#+id/et_search_bar_tap"
app:layout_constraintEnd_toEndOf="parent"/>
</androidx.constraintlayout.widget.ConstraintLayout>
</androidx.appcompat.widget.Toolbar>
BottomNavigationBehavior.kt
class BottomNavigationBehavior<V : View>(context: Context, attrs: AttributeSet) :
CoordinatorLayout.Behavior<V>(context, attrs) {
private var lastStartedType: Int = 0
private var offsetAnimator: ValueAnimator? = null
var isSnappingEnabled = false
override fun layoutDependsOn(parent: CoordinatorLayout, child: V, dependency: View): Boolean {
if (dependency is Snackbar.SnackbarLayout) {
updateSnackbar(child, dependency)
}
return super.layoutDependsOn(parent, child, dependency)
}
override fun onStartNestedScroll(
coordinatorLayout: CoordinatorLayout, child: V, directTargetChild: View, target: View, axes: Int, type: Int
): Boolean {
if (axes != ViewCompat.SCROLL_AXIS_VERTICAL)
return false
lastStartedType = type
offsetAnimator?.cancel()
return true
}
override fun onNestedPreScroll(
coordinatorLayout: CoordinatorLayout, child: V, target: View, dx: Int, dy: Int, consumed: IntArray, type: Int
) {
super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed, type)
child.translationY = max(0f, min(child.height.toFloat(), child.translationY + dy))
}
override fun onStopNestedScroll(coordinatorLayout: CoordinatorLayout, child: V, target: View, type: Int) {
if (!isSnappingEnabled)
return
// add snap behaviour
// Logic here borrowed from AppBarLayout onStopNestedScroll code
if (lastStartedType == ViewCompat.TYPE_TOUCH || type == ViewCompat.TYPE_NON_TOUCH) {
// find nearest seam
val currTranslation = child.translationY
val childHalfHeight = child.height * 0.5f
// translate down
if (currTranslation >= childHalfHeight) {
animateBarVisibility(child, isVisible = false)
}
// translate up
else {
animateBarVisibility(child, isVisible = true)
}
}
}
private fun animateBarVisibility(child: View, isVisible: Boolean) {
if (offsetAnimator == null) {
offsetAnimator = ValueAnimator().apply {
interpolator = DecelerateInterpolator()
duration = 150L
}
offsetAnimator?.addUpdateListener {
child.translationY = it.animatedValue as Float
}
} else {
offsetAnimator?.cancel()
}
val targetTranslation = if (isVisible) 0f else child.height.toFloat()
offsetAnimator?.setFloatValues(child.translationY, targetTranslation)
offsetAnimator?.start()
}
private fun updateSnackbar(child: View, snackbarLayout: Snackbar.SnackbarLayout) {
if (snackbarLayout.layoutParams is CoordinatorLayout.LayoutParams) {
val params = snackbarLayout.layoutParams as CoordinatorLayout.LayoutParams
params.anchorId = child.id
params.anchorGravity = Gravity.TOP
params.gravity = Gravity.TOP
snackbarLayout.layoutParams = params
}
}
}

So Finally Resolved My issue after getting my head around for 4 days here are some changes which I did and solved the issues :
activity_main.xml
<com.google.android.material.appbar.AppBarLayout
android:id="#+id/appbar"
android:layout_width="match_parent"
android:layout_height="?actionBarSize"
app:elevation="0dp"
android:background="#android:color/transparent"
app:layout_behavior="#string/appbar_scrolling_view_behavior"<!--Removed this line-->
>
<!--Bottom navigation view for the Selection of the Tabs and Items in Menu-->
<com.google.android.material.bottomnavigation.BottomNavigationView
app:layout_scrollFlags="scroll|enterAlways|snap"<!--Removed this line-->
android:id="#+id/browser_bottom_nav_view"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="bottom"
android:background="#ffff"
app:layout_behavior="com.example.android.browserui.BottomNavigationBehavior"
app:labelVisibilityMode="unlabeled"
app:menu="#menu/bottom_nav_menu"
/>
Here in activity_main.xml, I removed the layout_behavior because the appbar itself is invoking the scroll behavior for other layout items, it acts as a parent.
app:layout_behavior="#string/appbar_scrolling_view_behavior"
Also removed scrollflags from the bottom navigation view, AS I was implementing this behavior from the Class BottomNavigationBehavior.kt, You find the implementation below
app:layout_scrollFlags="scroll|enterAlways|snap"
browser_search_tap_tb.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.appcompat.widget.Toolbar
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="?actionBarSize"
android:background="#android:color/transparent"
app:layout_scrollFlags="scroll|enterAlways" <!--Removed this line-->
app:popupTheme="#style/ThemeOverlay.AppCompat"
app:contentInsetStart="8dp"
app:contentInsetEnd="8dp"
>
Here in browser_search_tb, I removed the following line because it was overriding the Scrollflags in co-ordinator layout so removed it and it worked flawlessly
app:layout_scrollFlags="scroll|enterAlways"
BottomNavigationBehavior.kt
override fun onStopNestedScroll(coordinatorLayout: CoordinatorLayout, child: V, target: View, type: Int) {
if (!isSnappingEnabled)
return // removed this line
{
// add snap behaviour
// Logic here borrowed from AppBarLayout onStopNestedScroll code
if (lastStartedType == ViewCompat.TYPE_TOUCH || type == ViewCompat.TYPE_NON_TOUCH) {
// find nearest seam
val currTranslation = child.translationY
val childHalfHeight = child.height * 0.5f
// translate down
if (currTranslation >= childHalfHeight) {
animateBarVisibility(child, isVisible = false)
}
// translate up
else {
animateBarVisibility(child, isVisible = true)
}
}
}
}
Here I removed the
return
and added braces{} to the if statement and snap feature did work properly
Hope this answer will help you and will cut down your debugging time.
The above reference is one of the best article you can find for scrolling behavior on the internet it simple and smooth to grasp

How to have a collapsing of top view into a smaller sized view?

This question was asked before in a too broad and unclear way here, so I've made it much more specific, with full explanation and code of what I've tried.
Background
I'm required to mimic the way the Google Calendar has a view at the top, that can animate and push down the view at the bottom, yet it has extra, different behavior. I've summarized what I'm trying to do on 3 characteristics:
Pressing on the toolbar will always work, to toggle expanding/collapsing of the top view, while having an arrow icon that changes its rotation. This is like on Google Calendar app.
The top view will always snap, just like on Google Calendar app.
When the top view is collapsed, only pressing on the toolbar will allow to expand it. This is like on Google Calendar app
When the top view is expanded, scrolling at the bottom view will only allow to collapse. If you try to scroll the other direction, nothing occurs, not even to the bottom view. This is like on Google Calendar app
Once collapsed, the top view will be replaced with a smaller view. This means it will always take some space, above the bottom view. This is not like on Google Calendar app, because on the Calendar app, the top view completely disappears once you collapse it.
Here's how Google Calendar app look like:
Scrolling on the bottom view also slowly hides the view at the top:
The problem
Using various solutions I've found in the past, I've succeeded to implement only a part of the needed behavior:
Having some UI in the toolbar is done by having some views in it, including the arrow view. For manual expanding/collapsing I use setExpanded on the AppBarLayout view. For the rotation of the arrow, I use a listener of how much the AppBarLayout has resized, using addOnOffsetChangedListener on it.
Snapping is easily done by adding snap value into layout_scrollFlags attribute of the CollapsingToolbarLayout. However, to make it really work well, without weird issues (reported here), I used this solution.
Blocking of affecting the top view when scrolling can be done by using the same code I've used on #2 (here), by calling setExpandEnabled there.
This works fine for when the top view is collapsed.
Similar to #3, but sadly, since it uses setNestedScrollingEnabled, which is in both directions, this works well only when the top view is collapsed. When it's expanded, it still allows the bottom view to scroll up, as opposed to Calendar app. When expanded, I need it to only allow to collapse, without allowing to really scroll.
Here's a demonstration of the good, and the bad:
This I've failed completely to do. I've tried a lot of solutions I've thought about, putting views in various places with various flags.
In short, I've succeeded doing 1-3, but not 4-5.
The code
Here's the current code (also available as whole project here) :
ScrollingActivity.kt
class ScrollingActivity : AppCompatActivity(), AppBarTracking {
private var mNestedView: MyRecyclerView? = null
private var mAppBarOffset: Int = 0
private var mAppBarIdle = false
private var mAppBarMaxOffset: Int = 0
private var isExpanded: Boolean = false
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_scrolling)
val toolbar = findViewById<Toolbar>(R.id.toolbar)
setSupportActionBar(toolbar)
mNestedView = findViewById(R.id.nestedView)
app_bar.addOnOffsetChangedListener({ appBarLayout, verticalOffset ->
mAppBarOffset = verticalOffset
val totalScrollRange = appBarLayout.totalScrollRange
val progress = (-verticalOffset).toFloat() / totalScrollRange
arrowImageView.rotation = 180 + progress * 180
isExpanded = verticalOffset == 0;
mAppBarIdle = mAppBarOffset >= 0 || mAppBarOffset <= mAppBarMaxOffset
if (mAppBarIdle)
setExpandAndCollapseEnabled(isExpanded)
})
app_bar.post(Runnable { mAppBarMaxOffset = -app_bar.totalScrollRange })
mNestedView!!.setAppBarTracking(this)
mNestedView!!.layoutManager = LinearLayoutManager(this)
mNestedView!!.adapter = object : RecyclerView.Adapter<RecyclerView.ViewHolder>() {
override fun getItemCount(): Int = 100
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
return object : ViewHolder(LayoutInflater.from(parent.context).inflate(android.R.layout.simple_list_item_1, parent, false)) {}
}
override fun onBindViewHolder(holder: ViewHolder, position: Int) {
(holder.itemView.findViewById<View>(android.R.id.text1) as TextView).text = "item $position"
}
}
expandCollapseButton.setOnClickListener({ v ->
isExpanded = !isExpanded
app_bar.setExpanded(isExpanded, true)
})
}
private fun setExpandAndCollapseEnabled(enabled: Boolean) {
mNestedView!!.isNestedScrollingEnabled = enabled
}
override fun isAppBarExpanded(): Boolean = mAppBarOffset == 0
override fun isAppBarIdle(): Boolean = mAppBarIdle
}
MyRecyclerView.kt
/**A RecyclerView that allows temporary pausing of casuing its scroll to affect appBarLayout, based on https://stackoverflow.com/a/45338791/878126 */
class MyRecyclerView #JvmOverloads constructor(context: Context, attrs: AttributeSet? = null, defStyle: Int = 0) : RecyclerView(context, attrs, defStyle) {
private var mAppBarTracking: AppBarTracking? = null
private var mView: View? = null
private var mTopPos: Int = 0
private var mLayoutManager: LinearLayoutManager? = null
interface AppBarTracking {
fun isAppBarIdle(): Boolean
fun isAppBarExpanded(): Boolean
}
override fun dispatchNestedPreScroll(dx: Int, dy: Int, consumed: IntArray?, offsetInWindow: IntArray?,
type: Int): Boolean {
if (type == ViewCompat.TYPE_NON_TOUCH && mAppBarTracking!!.isAppBarIdle()
&& isNestedScrollingEnabled) {
if (dy > 0) {
if (mAppBarTracking!!.isAppBarExpanded()) {
consumed!![1] = dy
return true
}
} else {
mTopPos = mLayoutManager!!.findFirstVisibleItemPosition()
if (mTopPos == 0) {
mView = mLayoutManager!!.findViewByPosition(mTopPos)
if (-mView!!.top + dy <= 0) {
consumed!![1] = dy - mView!!.top
return true
}
}
}
}
val returnValue = super.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow, type)
if (offsetInWindow != null && !isNestedScrollingEnabled && offsetInWindow[1] != 0)
offsetInWindow[1] = 0
return returnValue
}
override fun setLayoutManager(layout: RecyclerView.LayoutManager) {
super.setLayoutManager(layout)
mLayoutManager = layoutManager as LinearLayoutManager
}
fun setAppBarTracking(appBarTracking: AppBarTracking) {
mAppBarTracking = appBarTracking
}
}
ScrollingCalendarBehavior.kt
class ScrollingCalendarBehavior(context: Context, attrs: AttributeSet) : AppBarLayout.Behavior(context, attrs) {
override fun onInterceptTouchEvent(parent: CoordinatorLayout?, child: AppBarLayout?, ev: MotionEvent): Boolean = false
}
activity_scrolling.xml
<android.support.design.widget.CoordinatorLayout
android:id="#+id/coordinatorLayout" xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".ScrollingActivity">
<android.support.design.widget.AppBarLayout
android:id="#+id/app_bar" android:layout_width="match_parent" android:layout_height="wrap_content"
android:fitsSystemWindows="true" android:stateListAnimator="#null" android:theme="#style/AppTheme.AppBarOverlay"
app:expanded="false" app:layout_behavior="com.example.user.expandingtopviewtest.ScrollingCalendarBehavior"
tools:targetApi="lollipop">
<android.support.design.widget.CollapsingToolbarLayout
android:id="#+id/collapsingToolbarLayout" android:layout_width="match_parent"
android:layout_height="match_parent" android:fitsSystemWindows="true"
android:minHeight="?attr/actionBarSize" app:contentScrim="?attr/colorPrimary"
app:layout_scrollFlags="scroll|exitUntilCollapsed|snap" app:statusBarScrim="?attr/colorPrimaryDark">
<LinearLayout
android:layout_width="match_parent" android:layout_height="250dp"
android:layout_marginTop="?attr/actionBarSize" app:layout_collapseMode="parallax"
app:layout_collapseParallaxMultiplier="1.0">
<TextView
android:layout_width="match_parent" android:layout_height="match_parent" android:paddingLeft="10dp"
android:paddingRight="10dp" android:text="some large, expanded view"/>
</LinearLayout>
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar" android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize" app:layout_collapseMode="pin"
app:popupTheme="#style/AppTheme.PopupOverlay">
<android.support.constraint.ConstraintLayout
android:id="#+id/expandCollapseButton" android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize" android:background="?android:selectableItemBackground"
android:clickable="true" android:focusable="true" android:orientation="vertical">
<TextView
android:id="#+id/titleTextView" android:layout_width="wrap_content"
android:layout_height="wrap_content" android:layout_marginBottom="8dp"
android:layout_marginLeft="8dp" android:layout_marginStart="8dp" android:ellipsize="end"
android:gravity="center" android:maxLines="1" android:text="title"
android:textAppearance="#style/TextAppearance.Widget.AppCompat.Toolbar.Title"
android:textColor="#android:color/white" app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"/>
<ImageView
android:id="#+id/arrowImageView" android:layout_width="wrap_content" android:layout_height="0dp"
android:layout_marginLeft="8dp" android:layout_marginStart="8dp"
app:layout_constraintBottom_toBottomOf="#+id/titleTextView"
app:layout_constraintStart_toEndOf="#+id/titleTextView"
app:layout_constraintTop_toTopOf="#+id/titleTextView"
app:srcCompat="#android:drawable/arrow_down_float"
tools:ignore="ContentDescription,RtlHardcoded"/>
</android.support.constraint.ConstraintLayout>
</android.support.v7.widget.Toolbar>
</android.support.design.widget.CollapsingToolbarLayout>
</android.support.design.widget.AppBarLayout>
<com.example.user.expandingtopviewtest.MyRecyclerView
android:id="#+id/nestedView" android:layout_width="match_parent" android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior" tools:context=".ScrollingActivity"/>
</android.support.design.widget.CoordinatorLayout>
The questions
How can I make the scrolling being blocked when the top view is expanded, yet allow to collapse while scrolling ?
How can I make the top view be replaced with a smaller one when collapsed (and back to large one when expanded), instead of completely disappear ?
Update
Even though I've got the basic of what I asked about, there are still 2 issues with the current code (available on Github, here) :
The small view (the one you see on collapsed state) has inner views that need to have a clicking effect on them. When using the android:background="?attr/selectableItemBackgroundBorderless" on them, and clicking on this area while being expanded, the clicking is done on the small view. I've handled it by putting the small view on a different toolbar, but then the clicking effect doesn't get shown at all. I've written about this here, including sample project.
Here's the fix:
<android.support.design.widget.CoordinatorLayout
android:id="#+id/coordinatorLayout" xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".MainActivity">
<android.support.design.widget.AppBarLayout
android:id="#+id/app_bar" android:layout_width="match_parent" android:layout_height="wrap_content"
android:fitsSystemWindows="true" android:stateListAnimator="#null" android:theme="#style/AppTheme.AppBarOverlay"
app:expanded="false" app:layout_behavior="com.example.expandedtopviewtestupdate.ScrollingCalendarBehavior"
tools:targetApi="lollipop">
<android.support.design.widget.CollapsingToolbarLayout
android:id="#+id/collapsingToolbarLayout" android:layout_width="match_parent"
android:layout_height="match_parent" android:clipChildren="false" android:clipToPadding="false"
android:fitsSystemWindows="true" app:contentScrim="?attr/colorPrimary"
app:layout_scrollFlags="scroll|exitUntilCollapsed|snap|enterAlways"
app:statusBarScrim="?attr/colorPrimaryDark">
<!--large view -->
<LinearLayout
android:id="#+id/largeView" android:layout_width="match_parent" android:layout_height="280dp"
android:layout_marginTop="?attr/actionBarSize" android:orientation="vertical"
app:layout_collapseMode="parallax" app:layout_collapseParallaxMultiplier="1.0">
<TextView
android:id="#+id/largeTextView" android:layout_width="match_parent"
android:layout_height="match_parent" android:layout_gravity="center"
android:background="?attr/selectableItemBackgroundBorderless" android:clickable="true"
android:focusable="true" android:focusableInTouchMode="false" android:gravity="center"
android:text="largeView" android:textSize="14dp" tools:background="?attr/colorPrimary"
tools:layout_gravity="top|center_horizontal" tools:layout_height="40dp" tools:layout_width="40dp"
tools:text="1"/>
</LinearLayout>
<!--top toolbar-->
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar" android:layout_width="match_parent" android:layout_height="wrap_content"
android:layout_marginBottom="#dimen/small_view_height" app:contentInsetStart="0dp"
app:layout_collapseMode="pin" app:popupTheme="#style/AppTheme.PopupOverlay">
<android.support.constraint.ConstraintLayout
android:layout_width="match_parent" android:layout_height="wrap_content" android:clickable="true"
android:focusable="true">
<LinearLayout
android:id="#+id/expandCollapseButton" android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?android:selectableItemBackground" android:gravity="center_vertical"
android:orientation="horizontal" app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<TextView
android:id="#+id/titleTextView" android:layout_width="wrap_content"
android:layout_height="wrap_content" android:ellipsize="end" android:gravity="center"
android:maxLines="1" android:text="title"
android:textAppearance="#style/TextAppearance.Widget.AppCompat.Toolbar.Title"
android:textColor="#android:color/white"/>
<ImageView
android:id="#+id/arrowImageView" android:layout_width="wrap_content"
android:layout_height="wrap_content" android:layout_marginLeft="8dp"
android:layout_marginStart="8dp" app:srcCompat="#android:drawable/arrow_up_float"
tools:ignore="ContentDescription,RtlHardcoded"/>
</LinearLayout>
</android.support.constraint.ConstraintLayout>
</android.support.v7.widget.Toolbar>
<android.support.v7.widget.Toolbar
android:id="#+id/smallLayoutContainer" android:layout_width="match_parent"
android:layout_height="wrap_content" android:layout_marginTop="?attr/actionBarSize"
android:clipChildren="false" android:clipToPadding="false" app:contentInsetStart="0dp"
app:layout_collapseMode="pin">
<!--small view-->
<LinearLayout
android:id="#+id/smallLayout" android:layout_width="match_parent"
android:layout_height="#dimen/small_view_height" android:clipChildren="false"
android:clipToPadding="false" android:orientation="horizontal" tools:background="#ff330000"
tools:layout_height="#dimen/small_view_height">
<TextView
android:id="#+id/smallTextView" android:layout_width="match_parent"
android:layout_height="match_parent" android:layout_gravity="center"
android:background="?attr/selectableItemBackgroundBorderless" android:clickable="true"
android:focusable="true" android:focusableInTouchMode="false" android:gravity="center"
android:text="smallView" android:textSize="14dp" tools:background="?attr/colorPrimary"
tools:layout_gravity="top|center_horizontal" tools:layout_height="40dp"
tools:layout_width="40dp" tools:text="1"/>
</LinearLayout>
</android.support.v7.widget.Toolbar>
</android.support.design.widget.CollapsingToolbarLayout>
</android.support.design.widget.AppBarLayout>
<com.example.expandedtopviewtestupdate.MyRecyclerView
android:id="#+id/nestedView" android:layout_width="match_parent" android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior" tools:context=".ScrollingActivity"/>
</android.support.design.widget.CoordinatorLayout>
The Google Calendar allows to perform a scroll-down gesture on the toolbar itself, to trigger showing the month view. I've succeeded only adding a clicking event there, but not scrolling. Here's how it looks like:

Note: Full updated project is available here.
How can I make the scrolling being blocked when the top view is expanded, yet allow to collapse while scrolling ?
Issue #1: The RecyclerView should not be able to scroll at all when the app bar is not collapsed. To fix this, add enterAlways to the scroll flags for the CollapsingToolbarLayout as follows:
<android.support.design.widget.CollapsingToolbarLayout
android:id="#+id/collapsingToolbarLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clipChildren="false"
android:clipToPadding="false"
android:fitsSystemWindows="true"
app:layout_scrollFlags="scroll|exitUntilCollapsed|snap|enterAlways"
app:statusBarScrim="?attr/colorPrimaryDark">
enterAlways will not cause the app bar to open when closed since you are suppressing that functionality but works as desired otherwise.
Issue #2: When the app bar is fully expanded, the RecyclerView should not be allowed to scroll up. This happens to be a distinct issue from issue #1.
[Updated] To correct this, modify the behavior for the RecyclerView to consume scroll when the RecyclerView tries to scroll up and the app bar is fully expanded or will be fully expanded after the scroll(dy) is consumed . The RecyclerView can scroll up, but it never sees that action since its behavior, SlidingPanelBehavior, consumes the scroll. If the app bar is not fully expanded but will be expanded after the current scroll is consumed, the behavior forces the app bar to fully expand by calling modifying dy and calling the super before fully consuming the scroll. (See SlidingPanelBehavior#onNestedPreScroll()). (In the previous answer, the appBar behavior was modified. Putting the behavior change on RecyclerView is a better choice.)
Issue #3: Setting nested scrolling for the RecyclerView to enable/disabled when nested scrolling is already in the required state causes problems. To avoid these issues, only change the state of nested scrolling when a change is really being made with the following code change in ScrollingActivity:
private void setExpandAndCollapseEnabled(boolean enabled) {
if (mNestedView.isNestedScrollingEnabled() != enabled) {
mNestedView.setNestedScrollingEnabled(enabled);
}
}
This is how the test app behaves with the changes from above:
The changed modules with the above-mentioned changes are at the end of the post.
How can I make the top view be replaced with a smaller one when collapsed (and back to large one when expanded), instead of completely disappear ?
[Update] Make the smaller view a direct child of CollapsingToolbarLayout so it is a sibling of Toolbar. The following is a demonstration of this approach. The collapseMode of the smaller view is set to pin. The smaller view's margins as well as the margins of the toolbar are adjusted so the smaller view falls immediately below the toolbar. Since CollapsingToolbarLayout is a FrameLayout, views stack and the height of the FrameLayout just becomes the height of the tallest child view. This structure will avoid the issue where the insets needed adjustment and the problem with the missing click effect.
One final issue remains and that dragging the appbar down should open it with the assumption that dragging the smaller view down should not open the appbar. Permitting the appbar to open upon dragging is accomplished with setDragCallback of AppBarLayout.Behavior. Since the smaller view is incorporated into the appBar, dragging it down will open the appbar. To prevent this, a new behavior called MyAppBarBehavior is attached to the appbar. This behavior, in conjunction with code in the MainActivity prevents dragging of the smaller view to open the appbar but will permit the toolbar to be dragged.
activity_main.xml
<android.support.design.widget.CoordinatorLayout
android:id="#+id/coordinatorLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<android.support.design.widget.AppBarLayout
android:id="#+id/app_bar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:fitsSystemWindows="true"
android:stateListAnimator="#null"
android:theme="#style/AppTheme.AppBarOverlay"
app:expanded="false"
app:layout_behavior=".MyAppBarBehavior"
tools:targetApi="lollipop">
<android.support.design.widget.CollapsingToolbarLayout
android:id="#+id/collapsingToolbarLayout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:clipChildren="false"
android:clipToPadding="false"
android:fitsSystemWindows="true"
app:layout_scrollFlags="scroll|exitUntilCollapsed|snap|enterAlways"
app:statusBarScrim="?attr/colorPrimaryDark">
<!--large view -->
<LinearLayout
android:id="#+id/largeView"
android:layout_width="match_parent"
android:layout_height="280dp"
android:layout_marginTop="?attr/actionBarSize"
android:orientation="vertical"
app:layout_collapseMode="parallax"
app:layout_collapseParallaxMultiplier="1.0">
<TextView
android:id="#+id/largeTextView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="center"
android:background="?attr/selectableItemBackgroundBorderless"
android:clickable="true"
android:focusable="true"
android:focusableInTouchMode="false"
android:gravity="center"
android:text="largeView"
android:textSize="14dp"
tools:background="?attr/colorPrimary"
tools:layout_gravity="top|center_horizontal"
tools:layout_height="40dp"
tools:layout_width="40dp"
tools:text="1" />
</LinearLayout>
<!--top toolbar-->
<android.support.v7.widget.Toolbar
android:id="#+id/toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="#dimen/small_view_height"
app:contentInsetStart="0dp"
app:layout_collapseMode="pin"
app:popupTheme="#style/AppTheme.PopupOverlay">
<android.support.constraint.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:clickable="true"
android:focusable="true">
<LinearLayout
android:id="#+id/expandCollapseButton"
android:layout_width="match_parent"
android:layout_height="?attr/actionBarSize"
android:background="?android:selectableItemBackground"
android:gravity="center_vertical"
android:orientation="horizontal"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent">
<TextView
android:id="#+id/titleTextView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:ellipsize="end"
android:gravity="center"
android:maxLines="1"
android:text="title"
android:textAppearance="#style/TextAppearance.Widget.AppCompat.Toolbar.Title"
android:textColor="#android:color/white" />
<ImageView
android:id="#+id/arrowImageView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginLeft="8dp"
android:layout_marginStart="8dp"
app:srcCompat="#android:drawable/arrow_up_float"
tools:ignore="ContentDescription,RtlHardcoded" />
</LinearLayout>
</android.support.constraint.ConstraintLayout>
</android.support.v7.widget.Toolbar>
<!--small view-->
<LinearLayout
android:id="#+id/smallLayout"
android:layout_width="match_parent"
android:layout_height="#dimen/small_view_height"
android:layout_marginTop="?attr/actionBarSize"
android:clipChildren="false"
android:clipToPadding="false"
android:orientation="horizontal"
app:layout_collapseMode="pin"
tools:background="#ff330000"
tools:layout_height="#dimen/small_view_height">
<TextView
android:id="#+id/smallTextView"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="center"
android:background="?attr/selectableItemBackgroundBorderless"
android:clickable="true"
android:focusable="true"
android:focusableInTouchMode="false"
android:gravity="center"
android:text="smallView"
android:textSize="14dp"
tools:background="?attr/colorPrimary"
tools:layout_gravity="top|center_horizontal"
tools:layout_height="40dp"
tools:layout_width="40dp"
tools:text="1" />
</LinearLayout>
</android.support.design.widget.CollapsingToolbarLayout>
</android.support.design.widget.AppBarLayout>
<com.example.expandedtopviewtestupdate.MyRecyclerView
android:id="#+id/nestedView"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="#string/appbar_scrolling_view_behavior"
tools:context=".SlidingPanelBehavior" />
</android.support.design.widget.CoordinatorLayout>
Finally, in the addOnOffsetChangedListener add the following code to fade out/fade in the smaller view as the app bar expands and contracts. Once the view's alpha is zero (invisible), set its visibility to View.INVISIBLE so it can't be clicked. Once the view's alpha increases above zero, make it visible and clickable by setting its visibility to View.VISIBLE.
mSmallLayout.setAlpha((float) -verticalOffset / totalScrollRange);
// If the small layout is not visible, make it officially invisible so
// it can't receive clicks.
if (alpha == 0) {
mSmallLayout.setVisibility(View.INVISIBLE);
} else if (mSmallLayout.getVisibility() == View.INVISIBLE) {
mSmallLayout.setVisibility(View.VISIBLE);
}
Here are the results:
Here are the new modules with all of the above changes incorporated.
MainActivity.java
public class MainActivity extends AppCompatActivity
implements MyRecyclerView.AppBarTracking {
private MyRecyclerView mNestedView;
private int mAppBarOffset = 0;
private boolean mAppBarIdle = true;
private int mAppBarMaxOffset = 0;
private AppBarLayout mAppBar;
private boolean mIsExpanded = false;
private ImageView mArrowImageView;
private LinearLayout mSmallLayout;
#Override
protected void onCreate(Bundle savedInstanceState) {
LinearLayout expandCollapse;
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Toolbar toolbar = findViewById(R.id.toolbar);
expandCollapse = findViewById(R.id.expandCollapseButton);
mArrowImageView = findViewById(R.id.arrowImageView);
mNestedView = findViewById(R.id.nestedView);
mAppBar = findViewById(R.id.app_bar);
mSmallLayout = findViewById(R.id.smallLayout);
// Log when the small text view is clicked
findViewById(R.id.smallTextView).setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Log.d(TAG, "<<<<click small layout");
}
});
// Log when the big text view is clicked.
findViewById(R.id.largeTextView).setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Log.d(TAG, "<<<<click big view");
}
});
setSupportActionBar(toolbar);
ActionBar ab = getSupportActionBar();
if (ab != null) {
getSupportActionBar().setDisplayShowTitleEnabled(false);
}
mAppBar.post(new Runnable() {
#Override
public void run() {
mAppBarMaxOffset = -mAppBar.getTotalScrollRange();
CoordinatorLayout.LayoutParams lp =
(CoordinatorLayout.LayoutParams) mAppBar.getLayoutParams();
MyAppBarBehavior behavior = (MyAppBarBehavior) lp.getBehavior();
// Only allow drag-to-open if the drag touch is on the toolbar.
// Once open, all drags are allowed.
if (behavior != null) {
behavior.setCanOpenBottom(findViewById(R.id.toolbar).getHeight());
}
}
});
mNestedView.setAppBarTracking(this);
mNestedView.setLayoutManager(new LinearLayoutManager(this));
mNestedView.setAdapter(new RecyclerView.Adapter<RecyclerView.ViewHolder>() {
#Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
return new ViewHolder(
LayoutInflater.from(parent.getContext())
.inflate(android.R.layout.simple_list_item_1, parent, false));
}
#SuppressLint("SetTextI18n")
#Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
((TextView) holder.itemView.findViewById(android.R.id.text1))
.setText("Item " + position);
}
#Override
public int getItemCount() {
return 200;
}
class ViewHolder extends RecyclerView.ViewHolder {
public ViewHolder(View view) {
super(view);
}
}
});
mAppBar.addOnOffsetChangedListener(new AppBarLayout.OnOffsetChangedListener() {
#Override
public void onOffsetChanged(AppBarLayout appBarLayout, int verticalOffset) {
mAppBarOffset = verticalOffset;
int totalScrollRange = appBarLayout.getTotalScrollRange();
float progress = (float) (-verticalOffset) / (float) totalScrollRange;
mArrowImageView.setRotation(-progress * 180);
mIsExpanded = verticalOffset == 0;
mAppBarIdle = mAppBarOffset >= 0 || mAppBarOffset <= mAppBarMaxOffset;
float alpha = (float) -verticalOffset / totalScrollRange;
mSmallLayout.setAlpha(alpha);
// If the small layout is not visible, make it officially invisible so
// it can't receive clicks.
if (alpha == 0) {
mSmallLayout.setVisibility(View.INVISIBLE);
} else if (mSmallLayout.getVisibility() == View.INVISIBLE) {
mSmallLayout.setVisibility(View.VISIBLE);
}
}
});
expandCollapse.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
setExpandAndCollapseEnabled(true);
if (mIsExpanded) {
setExpandAndCollapseEnabled(false);
}
mIsExpanded = !mIsExpanded;
mNestedView.stopScroll();
mAppBar.setExpanded(mIsExpanded, true);
}
});
}
private void setExpandAndCollapseEnabled(boolean enabled) {
if (mNestedView.isNestedScrollingEnabled() != enabled) {
mNestedView.setNestedScrollingEnabled(enabled);
}
}
#Override
public boolean isAppBarExpanded() {
return mAppBarOffset == 0;
}
#Override
public boolean isAppBarIdle() {
return mAppBarIdle;
}
private static final String TAG = "MainActivity";
}
SlidingPanelBehavior.java
public class SlidingPanelBehavior extends AppBarLayout.ScrollingViewBehavior {
private AppBarLayout mAppBar;
public SlidingPanelBehavior() {
super();
}
public SlidingPanelBehavior(Context context, AttributeSet attrs) {
super(context, attrs);
}
#Override
public boolean layoutDependsOn(final CoordinatorLayout parent, View child, View dependency) {
if (mAppBar == null && dependency instanceof AppBarLayout) {
// Capture our appbar for later use.
mAppBar = (AppBarLayout) dependency;
}
return dependency instanceof AppBarLayout;
}
#Override
public boolean onInterceptTouchEvent(CoordinatorLayout parent, View child, MotionEvent event) {
int action = event.getAction();
if (event.getAction() != MotionEvent.ACTION_DOWN) { // Only want "down" events
return false;
}
if (getAppBarLayoutOffset(mAppBar) == -mAppBar.getTotalScrollRange()) {
// When appbar is collapsed, don't let it open through nested scrolling.
setNestedScrollingEnabledWithTest((NestedScrollingChild2) child, false);
} else {
// Appbar is partially to fully expanded. Set nested scrolling enabled to activate
// the methods within this behavior.
setNestedScrollingEnabledWithTest((NestedScrollingChild2) child, true);
}
return false;
}
#Override
public boolean onStartNestedScroll(#NonNull CoordinatorLayout coordinatorLayout, #NonNull View child,
#NonNull View directTargetChild, #NonNull View target,
int axes, int type) {
//noinspection RedundantCast
return ((NestedScrollingChild2) child).isNestedScrollingEnabled();
}
#Override
public void onNestedPreScroll(#NonNull CoordinatorLayout coordinatorLayout, #NonNull View child,
#NonNull View target, int dx, int dy, #NonNull int[] consumed,
int type) {
// How many pixels we must scroll to fully expand the appbar. This value is <= 0.
final int appBarOffset = getAppBarLayoutOffset(mAppBar);
// Check to see if this scroll will expand the appbar 100% or collapse it fully.
if (dy <= appBarOffset) {
// Scroll by the amount that will fully expand the appbar and dispose of the rest (dy).
super.onNestedPreScroll(coordinatorLayout, mAppBar, target, dx,
appBarOffset, consumed, type);
consumed[1] += dy;
} else if (dy >= (mAppBar.getTotalScrollRange() + appBarOffset)) {
// This scroll will collapse the appbar. Collapse it and dispose of the rest.
super.onNestedPreScroll(coordinatorLayout, mAppBar, target, dx,
mAppBar.getTotalScrollRange() + appBarOffset,
consumed, type);
consumed[1] += dy;
} else {
// This scroll will leave the appbar partially open. Just do normal stuff.
super.onNestedPreScroll(coordinatorLayout, child, target, dx, dy, consumed, type);
}
}
/**
* {#code onNestedPreFling()} is overriden to address a nested scrolling defect that was
* introduced in API 26. This method prevent the appbar from misbehaving when scrolled/flung.
* <p>
* Refer to "Bug in design support library"
*/
#Override
public boolean onNestedPreFling(#NonNull CoordinatorLayout coordinatorLayout,
#NonNull View child, #NonNull View target,
float velocityX, float velocityY) {
//noinspection RedundantCast
if (((NestedScrollingChild2) child).isNestedScrollingEnabled()) {
// Just stop the nested fling and let the appbar settle into place.
((NestedScrollingChild2) child).stopNestedScroll(ViewCompat.TYPE_NON_TOUCH);
return true;
}
return super.onNestedPreFling(coordinatorLayout, child, target, velocityX, velocityY);
}
private static int getAppBarLayoutOffset(AppBarLayout appBar) {
final CoordinatorLayout.Behavior behavior =
((CoordinatorLayout.LayoutParams) appBar.getLayoutParams()).getBehavior();
if (behavior instanceof AppBarLayout.Behavior) {
return ((AppBarLayout.Behavior) behavior).getTopAndBottomOffset();
}
return 0;
}
// Something goes amiss when the flag it set to its current value, so only call
// setNestedScrollingEnabled() if it will result in a change.
private void setNestedScrollingEnabledWithTest(NestedScrollingChild2 child, boolean enabled) {
if (child.isNestedScrollingEnabled() != enabled) {
child.setNestedScrollingEnabled(enabled);
}
}
#SuppressWarnings("unused")
private static final String TAG = "SlidingPanelBehavior";
}
MyRecyclerView.kt
/**A RecyclerView that allows temporary pausing of casuing its scroll to affect appBarLayout, based on https://stackoverflow.com/a/45338791/878126 */
class MyRecyclerView #JvmOverloads constructor(context: Context, attrs: AttributeSet? = null, defStyle: Int = 0) : RecyclerView(context, attrs, defStyle) {
private var mAppBarTracking: AppBarTracking? = null
private var mView: View? = null
private var mTopPos: Int = 0
private var mLayoutManager: LinearLayoutManager? = null
interface AppBarTracking {
fun isAppBarIdle(): Boolean
fun isAppBarExpanded(): Boolean
}
override fun dispatchNestedPreScroll(dx: Int, dy: Int, consumed: IntArray?, offsetInWindow: IntArray?, type: Int): Boolean {
if (type == ViewCompat.TYPE_NON_TOUCH && mAppBarTracking!!.isAppBarIdle()
&& isNestedScrollingEnabled) {
if (dy > 0) {
if (mAppBarTracking!!.isAppBarExpanded()) {
consumed!![1] = dy
return true
}
} else {
mTopPos = mLayoutManager!!.findFirstVisibleItemPosition()
if (mTopPos == 0) {
mView = mLayoutManager!!.findViewByPosition(mTopPos)
if (-mView!!.top + dy <= 0) {
consumed!![1] = dy - mView!!.top
return true
}
}
}
}
if (dy < 0 && type == ViewCompat.TYPE_TOUCH && mAppBarTracking!!.isAppBarExpanded()) {
consumed!![1] = dy
return true
}
val returnValue = super.dispatchNestedPreScroll(dx, dy, consumed, offsetInWindow, type)
if (offsetInWindow != null && !isNestedScrollingEnabled && offsetInWindow[1] != 0)
offsetInWindow[1] = 0
return returnValue
}
override fun setLayoutManager(layout: RecyclerView.LayoutManager) {
super.setLayoutManager(layout)
mLayoutManager = layoutManager as LinearLayoutManager
}
fun setAppBarTracking(appBarTracking: AppBarTracking) {
mAppBarTracking = appBarTracking
}
override fun fling(velocityX: Int, velocityY: Int): Boolean {
var velocityY = velocityY
if (!mAppBarTracking!!.isAppBarIdle()) {
val vc = ViewConfiguration.get(context)
velocityY = if (velocityY < 0) -vc.scaledMinimumFlingVelocity
else vc.scaledMinimumFlingVelocity
}
return super.fling(velocityX, velocityY)
}
}
MyAppBarBehavior.java
/**
* Attach this behavior to AppBarLayout to disable the bottom portion of a closed appBar
* so it cannot be touched to open the appBar. This behavior is helpful if there is some
* portion of the appBar that displays when the appBar is closed, but should not open the appBar
* when the appBar is closed.
*/
public class MyAppBarBehavior extends AppBarLayout.Behavior {
// Touch above this y-axis value can open the appBar.
private int mCanOpenBottom;
// Determines if the appBar can be dragged open or not via direct touch on the appBar.
private boolean mCanDrag = true;
#SuppressWarnings("unused")
public MyAppBarBehavior() {
init();
}
#SuppressWarnings("unused")
public MyAppBarBehavior(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
private void init() {
setDragCallback(new AppBarLayout.Behavior.DragCallback() {
#Override
public boolean canDrag(#NonNull AppBarLayout appBarLayout) {
return mCanDrag;
}
});
}
#Override
public boolean onInterceptTouchEvent(CoordinatorLayout parent,
AppBarLayout child,
MotionEvent event) {
if (event.getAction() == MotionEvent.ACTION_DOWN) {
// If appBar is closed. Only allow scrolling in defined area.
if (child.getTop() <= -child.getTotalScrollRange()) {
mCanDrag = event.getY() < mCanOpenBottom;
}
}
return super.onInterceptTouchEvent(parent, child, event);
}
public void setCanOpenBottom(int bottom) {
mCanOpenBottom = bottom;
}
}

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